Extend Org heading background face past the newline?

Hello everyone. Currently, I am running the latest version of Org, with text properties and the `master` branch of Emacs. I am using `modus-themes` as well. By using (with-eval-after-load 'org (dolist (face '(org-block org-block-begin-line org-block-end-line org-level-1 org-level-2 org-level-3 org-level-4 org-level-5 org-level-6 org-level-7 org-level-8 org-quote org-hide)) (set-face-attribute face nil :extend t))) I can extend the background on the Org headline past the newline when unfolded, but not when folded. The package [https://github.com/tarsius/backline/blob/master/backline.el](https://github.com/tarsius/backline/blob/master/backline.el) addresses this for `outline-mode` but now Org mode uses text properties so that package does not work for Org mode.

Have you tried setting the variable org-fontify-whole-heading-line to true?

Yes.

This is because the trailing newline in the folded heading gets hidden. If the trailing newline is invisible, :extend t has no effect. It is Emacs limitation, AFAIK. Probably, you need to write a feature request/bug repor to emacs-devel. You can, for example, use M-x report-emacs-bug to create the email template for your feature request.